On Friday 12 February 2021 11:17:36 Jon Elson wrote: > On 02/11/2021 09:41 PM, Gene Heskett wrote: > > Well, it takes FF1 = 20.5 to get a cruise at about null, > > And I did have FF2 = .5, but .35 cancels the stop spike. > > > > So my question is why are these so far out of the normal range where > > for a stepgen FF1=1.0 and FF2 = .001 is about right. Something else > > must be seriously out of whack. But what? > > Well, I have no idea, I just know what WORKS, by trial and > error (and a little knowledge of the > control theory behind it.) > > > pid_A.output is almost straight to > > the pwmgen.A.value, with that pwmgen in mode 2. An idb in the middle > > of the link seems to be without measurable effect, but maybe I've > > not tried a high enough idb.amount. That is currantly at 10, a value > > I would think would make it overshoot and oscillate but does not. > > I have no idea what hardware you have cobbled up, so I > really don't know what is going on.
The only thing I'll fault this motor for is that its an oilite bushing and brushed, both of which add friction/stiction in unk quantities. Its also two worms in series, one in this motor and the one in the bs-1. The pid almost copes but the approach to null is never quite done UNLESS the PID winds up. In which case it does overshoot and goes into reverse, often crowbarring the psu, which will then shutdown till it cools again. Takes 2 to 3 minutes for it to cool enough to restart. 100 watt motor, only a 400 watt 24v supply. My next tune session will reduce the pid's max_output until I see it actually slowing, which should stop the windup. I thought 900 would be too low, but it still starts to wind up at about 1800 degrees a minute, so there is not a known relationship there either. Thanks, Jon Cheers, Gene Heskett -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) If we desire respect for the law, we must first make the law respectable. - Louis D. Brandeis Genes Web page <http://geneslinuxbox.net:6309/gene> _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
